automobile

Compared meaning: a motor vehicle used for transport (noun).

比较义项：汽车（名词）。

• car

  The ordinary, all-purpose word for this vehicle in everyday speech; neutral in tone and used in almost every context, unlike the more formal, slangy, or compound-bound alternatives.

  最普通、最常用的说法，几乎适用于所有语境，语气中性；其余三个词在日常口语中会显得过于正式、俚语化或只用于复合词。

  Can you give me a ride home in your car after work?

  下班后你能开车送我回家吗？

• machine

  Informal, especially in American English, used to admire a car's power, speed, or style; rarely appears in neutral or technical writing, unlike the plainer or more formal alternatives.

  非正式说法，尤其在美式英语中使用，常带着对车辆动力、速度或外形的欣赏语气，很少出现在中性或技术性文本中；其余三个词都没有这种“炫酷座驾”的意味。

  That's a beautiful machine you've got there — how fast does it go?

  你这辆车真漂亮——能跑多快呢？

• automobile 本词

  Formal and somewhat technical, American English, common in industry, legal, or written contexts; sounds stiff or old-fashioned in casual conversation compared with the other three.

  正式、略带技术色彩的说法，属于美式英语，常见于行业、法律或书面语境；用在日常口语里会显得生硬、老派，不如其余三个词自然。

  The automobile industry has invested billions in electric vehicle technology this decade.

  这十年来，汽车行业已在电动汽车技术上投入了数十亿美元。

• auto

  Informal, mainly American, almost always used inside a compound noun such as auto shop or auto insurance rather than standing alone; alone it sounds dated or like a headline.

  非正式说法，主要用于美式英语，几乎总是出现在复合名词中，如 auto shop（汽修店）、auto insurance（汽车保险），很少单独使用；单独使用时会显得过时，像新闻标题的用语。

  He works at an auto shop fixing cars every weekend.

  他每个周末都在一家汽车修理厂修车。

All four mean a car. Car is ordinary, everyday, used in any context. Automobile is formal, technical, common in American industry writing. Auto is informal, almost always part of a compound like auto shop. Machine is informal, admiring the car. Excludes machine meaning 'a device'.

这四个词在“汽车”这一意义上相近，但语气和使用场合不同：car 最普通、最常用；automobile 比较正式，多见于书面或行业语境；auto 几乎总是出现在复合词里；machine 是非正式说法，带有对车辆动力或外形的赞赏语气。这里不比较 machine 表示“机器”的普通义项。